package com.omniseckill.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.omniseckill.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.annotation.Id;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.yaml.snakeyaml.events.Event;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Slf4j
@Component
public class CacheClient {

    private StringRedisTemplate stringRedisTemplate;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    /**
     * 缓存穿透
     */
    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if (json != null){
            //返回一个错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在，写入redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }

    /**
     * 缓存击穿——逻辑过期
     */
    public <R, ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)){
            //3.未命中，返回空值
            return null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断缓存是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1 未过期，直接返回店铺信息
            return r;
        }
        //5.2 已过期，需要缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2 判断是否获取互斥锁成功
        //6.3 成功，开启独立线程，实现缓存重建
        if (isLock){
            CACHE_REBUILD_EXECUTOR.submit(() -> {

                try {
                    //查询数据库
                    R apply = dbFallback.apply(id);
                    //缓存重建
                    this.setWithLogicalExpire(key, apply, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unLock(lockKey);
                }
            });
        }
        //6.4 返回过期的商铺信息
        return r;
    }

    /**
     * 缓存击穿——互斥锁
     */
    public <R,ID> R queryWithMutex(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        R r=null;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值(穿透)
        if (json != null){
            //返回一个错误信息
            return null;
        }
        //4.实现缓存重构
        //4.1 获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2 判断是否获取互斥锁成功
            if (!isLock){
                //4.3 不成功，休眠重新尝试
                Thread.sleep(50);
                return queryWithMutex(keyPrefix,id,type,dbFallback,time,unit);//递归调用
            }
            //4.4 成功，根据id查询数据库
            r = dbFallback.apply(id);
            //模拟重建的延迟
            Thread.sleep(200);
            //5.不存在，返回错误
            if (r == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
            //6.存在，写入redis
            this.set(key,r,time,unit);
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unLock(lockKey);
        }
        //8.返回
        return r;
    }

    /**
     * 获取锁
     */
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 释放锁
     */
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
}
